From: zhong jiang zhongjiang@huawei.com Subject: mm: fix trying to reclaim unevictable lru page when calling madvise_pageout

Recently, I hit the following issue when running upstream.

kernel BUG at mm/vmscan.c:1521! invalid opcode: 0000 [#1] SMP KASAN PTI CPU: 0 PID: 23385 Comm: syz-executor.6 Not tainted 5.4.0-rc4+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 RIP: 0010:shrink_page_list+0x12b6/0x3530 mm/vmscan.c:1521 Code: de f5 ff ff e8 ab 79 eb ff 4c 89 f7 e8 43 33 0d 00 e9 cc f5 ff ff e8 99 79 eb ff 48 c7 c6 a0 34 2b a0 4c 89 f7 e8 1a 4d 05 00 <0f> 0b e8 83 79 eb ff 48 89 d8 48 c1 e8 03 42 80 3c 38 00 0f 85 74 RSP: 0018:ffff88819a3df5a0 EFLAGS: 00010286 RAX: 0000000000040000 RBX: ffffea00061c3980 RCX: ffffffff814fba36 RDX: 00000000000056f7 RSI: ffffc9000c02c000 RDI: ffff8881f70268cc RBP: ffff88819a3df898 R08: ffffed103ee05de0 R09: ffffed103ee05de0 R10: 0000000000000001 R11: ffffed103ee05ddf R12: ffff88819a3df6f0 R13: ffff88819a3df6f0 R14: ffffea00061c3980 R15: dffffc0000000000 FS: 00007f21b9d8e700(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b2d621000 CR3: 00000001c8c46004 CR4: 00000000007606f0 DR0: 0000000020000140 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600 PKRU: 55555554 Call Trace: reclaim_pages+0x499/0x800 mm/vmscan.c:2188 madvise_cold_or_pageout_pte_range+0x58a/0x710 mm/madvise.c:453 walk_pmd_range mm/pagewalk.c:53 [inline] walk_pud_range mm/pagewalk.c:112 [inline] walk_p4d_range mm/pagewalk.c:139 [inline] walk_pgd_range mm/pagewalk.c:166 [inline] __walk_page_range+0x45a/0xc20 mm/pagewalk.c:261 walk_page_range+0x179/0x310 mm/pagewalk.c:349 madvise_pageout_page_range mm/madvise.c:506 [inline] madvise_pageout+0x1f0/0x330 mm/madvise.c:542 madvise_vma mm/madvise.c:931 [inline] __do_sys_madvise+0x7d2/0x1600 mm/madvise.c:1113 do_syscall_64+0x9f/0x4c0 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe

madvise_pageout() accesses the specified range of the vma and isolates them, then runs shrink_page_list() to reclaim its memory. But it also isolates the unevictable pages to reclaim. Hence, we can catch the cases in shrink_page_list().

The root cause is that we scan the page tables instead of specific LRU list. and so we need to filter out the unevictable lru pages from our end.

Link: http://lkml.kernel.org/r/1572616245-18946-1-git-send-email-zhongjiang@huawei... Fixes: 1a4e58cce84e ("mm: introduce MADV_PAGEOUT") Signed-off-by: zhong jiang zhongjiang@huawei.com Suggested-by: Johannes Weiner hannes@cmpxchg.org Acked-by: Johannes Weiner hannes@cmpxchg.org Acked-by: Minchan Kim minchan@kernel.org Acked-by: Michal Hocko mhocko@suse.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/madvise.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-)

--- a/mm/madvise.c~mm-fix-trying-to-reclaim-unevictable-lru-page-when-calling-madvise_pageout +++ a/mm/madvise.c @@ -363,8 +363,12 @@ static int madvise_cold_or_pageout_pte_r ClearPageReferenced(page); test_and_clear_page_young(page); if (pageout) { - if (!isolate_lru_page(page)) - list_add(&page->lru, &page_list); + if (!isolate_lru_page(page)) { + if (PageUnevictable(page)) + putback_lru_page(page); + else + list_add(&page->lru, &page_list); + } } else deactivate_page(page); huge_unlock: @@ -441,8 +445,12 @@ regular_page: ClearPageReferenced(page); test_and_clear_page_young(page); if (pageout) { - if (!isolate_lru_page(page)) - list_add(&page->lru, &page_list); + if (!isolate_lru_page(page)) { + if (PageUnevictable(page)) + putback_lru_page(page); + else + list_add(&page->lru, &page_list); + } } else deactivate_page(page); } _